1. Field of the Invention
This invention relates to the field of the cord-locking devices to lock the cord or cords controlling pleated shades, venetian blinds and similar blind and shade constructions. In particular, it relates to an improved cord-locking device comprising a channel member and a housing to permit the cord to be easily threaded into the channel member and then covered by the housing.
2. Prior Art
Cord-locking devices for venetian blinds frequently include teeth on a pivotally mounted member over which the cord runs. In normal use the cord may consist of two portions looped together to run closely parallel to each other, or it may include two separate cords running closely parallel to each other through the cord-locking device. By pulling on the cord or cords in the proper direction, the teeth can be caused to become disengaged from the cord or cords, and the member on which the teeth are formed may be caused to pivot out of the way so that the position of the venetian blind can be changed, for example by raising or lowering it. When it is desired to lock the blind in position, the person manipulating the blind brings the cord or cords into another position to engage the teeth of the locking device and draw those teeth into the locking position in which the cord or cords will be held by strong frictional engagement between the teeth of the locking device and a fixed portion of that device.
A locking device of the type just described has the disadvantage that it causes wear on the cord or cords due to the sharp points of the teeth and is frequently difficult to manipulate.
Another form of locking device is that shown in U.S. Pat. Nos. 3,191,664 and 3,221,802 in which there are two pivotally mounted members, both being generally U-shaped and one embracing the other. The inner of the two members has a slot through which the cords pass into a region between that member and the outer member. When the cords are pulled to raise the venetian blind, the two pivotally mounted members are separated from each other, which frees the cords to move. When the blind is to be locked in position, a small frictional engagement between the cords and the inner member allows the cords to draw the inner member up sufficiently into alignment with the outer member to provide a wedging action that grips the cords and holds them firmly in place by virtue of the tension supplied by the weight of the venetian blind.
The structure described and shown in those patents has the axle for the locking members fixedly mounted in a folded, U-shaped bracket made of sheet metal. That axle is located parallel to the axle of a guide pulley around which the cords curve from a horizontal direction to a vertical direction and thus perpendicular to any run of the cord. A housing over the bracket would make it difficult to thread the cords through the locking and guiding mechanism, and the patents do not suggest any such housing.